[libvirt PATCH v6 35/36] run: add ability to set selinux context

When running libvirt from the build directory with the 'run' script, it will run as unconfined_t. This can result in unexpected behavior when selinux is enforcing due to the fact that the selinux policies are written assuming that libvirt is running with the system_u:system_r:virtd_t context. This patch adds a new --selinux option to the run script. When this option is specified, it will launch the specified binary using the 'runcon' utility to set its selinux context to the one mentioned above. Since this may require root privileges, setting the selinux context is not the default behavior and must be enabled with the command line switch. Signed-off-by: Jonathon Jongsma <jjongsma(a)redhat.com&gt; --- run.in | 100 +++++++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 80 insertions(+), 20 deletions(-) diff --git a/run.in b/run.in index 80a5d2dd43..5b89b3dcd5 100644 --- a/run.in +++ b/run.in @@ -40,9 +40,11 @@ # # ---------------------------------------------------------------------- +import argparse import os import os.path import random +import shutil import signal import subprocess import sys @@ -59,15 +61,20 @@ def prepend(env, varname, extradir): here = "@abs_builddir@" -if len(sys.argv) < 2: - print("syntax: %s BINARY [ARGS...]" % sys.argv[0], file=sys.stderr) +parser = argparse.ArgumentParser(add_help=False, allow_abbrev=False) +parser.add_argument('--selinux', + action='store_true', + help='Run in the appropriate selinux context') + +opts, args = parser.parse_known_args() + +if len(args) < 1: + print("syntax: %s [--selinux] BINARY [ARGS...]" % sys.argv[0], file=sys.stderr) sys.exit(1) -prog = sys.argv[1] -args = sys.argv[1:] +prog = args[0] env = os.environ - prepend(env, "LD_LIBRARY_PATH", os.path.join(here, "src")) prepend(env, "PKG_CONFIG_PATH", os.path.join(here, "src")) prepend(env, "PATH", os.path.join(here, "tools")) @@ -130,10 +137,25 @@ def change_unit(name, action): return ret == 0 +def chcon(path, user, role, type): + print("Setting file context of {} to u={}, r={}, t={}...".format(progpath, + user, + role, + type)) + ret = subprocess.call(["chcon", "-u", user, "-r", role, "-t", type, path]) + return ret == 0 + + +def restorecon(path): + print("Restoring selinux context for {}...".format(path)) + ret = subprocess.call(["restorecon", path]) + return ret == 0 + + try_stop_units = [] if is_systemd_host(): maybe_stopped_units = [] - for arg in sys.argv: + for arg in args: name = os.path.basename(arg) if is_modular_daemon(name): # Only need to stop libvirtd or this specific modular unit @@ -149,11 +171,10 @@ if is_systemd_host(): if is_unit_active(unit): try_stop_units.append(unit) -if len(try_stop_units) == 0: +if len(try_stop_units) == 0 and not opts.selinux: # Run the program directly, replacing ourselves os.execvpe(prog, args, env) else: - print("Temporarily stopping systemd units...") stopped_units = [] def sighandler(signum, frame): @@ -164,12 +185,48 @@ else: signal.signal(signal.SIGQUIT, sighandler) try: - for unit in try_stop_units: - print(" > %s" % unit) - if not change_unit(unit, "stop"): - raise Exception("Unable to stop '%s'" % unit) - - stopped_units.append(unit) + dorestorecon = False + progpath = shutil.which(prog) + if len(try_stop_units): + print("Temporarily stopping systemd units...") + + for unit in try_stop_units: + print(" > %s" % unit) + if not change_unit(unit, "stop"): + raise Exception("Unable to stop '%s'" % unit) + + stopped_units.append(unit) + + if opts.selinux: + # if using a wrapper command like 'gdb', setting the selinux + # context won't work because the wrapper command will not be a + # valid entrypoint for the virtd_t context + if os.path.basename(prog) not in ["libvirtd", *modular_daemons]: + raise Exception("'{}' is not recognized as a valid daemon. " + "Selinux process context can only be set when " + "executing a daemon directly without wrapper " + "commands".format(prog)) + + if not progpath: + raise Exception("Can't find executable {} for selinux labeling" + .format(prog)) + + if not progpath.startswith(os.path.abspath(here)): + raise Exception("Refusing to change selinux context of file " + "'{}' outside build directory" + .format(progpath)) + + # selinux won't allow us to transition to the virtd_t context from + # e.g. the user_home_t context (the likely label of the local + # executable file) + if not chcon(progpath, "system_u", "object_r", "virtd_exec_t"): + raise Exception("Failed to change selinux context of binary") + dorestorecon = True + + args = ['runcon', + '-u', 'system_u', + '-r', 'system_r', + '-t', 'virtd_t', *args] print("Running '%s'..." % str(" ".join(args))) ret = subprocess.call(args, env=env) @@ -178,9 +235,12 @@ else: except Exception as e: print("%s" % e, file=sys.stderr) finally: - print("Re-starting original systemd units...") - stopped_units.reverse() - for unit in stopped_units: - print(" > %s" % unit) - if not change_unit(unit, "start"): - print(" ! unable to restart %s" % unit, file=sys.stderr) + if len(stopped_units): + print("Re-starting original systemd units...") + stopped_units.reverse() + for unit in stopped_units: + print(" > %s" % unit) + if not change_unit(unit, "start"): + print(" ! unable to restart %s" % unit, file=sys.stderr) + if dorestorecon: + restorecon(progpath) -- 2.41.0